[Jamo]

I've lived with both, a Tremec 5 spd with a 351C and a toploader with the current big block. Some observations....

I miss the short throw of the Tremec.

I love the feeling of strength with the toploader...knowing it's probably gonna be the last thing that breaks on this car. Part of that comes with dealing with Kee.

I did like the lower rpms with the Tremec (3.54s), but it really didn't matter on day to day drives. Always downshifted for oomph anyway. Course, the Cleveland was a high winding SOB.

I'm running 3.31s with the stroked Shelby block and toploader, and it has been very nice. Every gear is usable, and I'm not downshifting very often to find a gear. Second gear takes me around most autocross courses (shifting wastes time).

Gas mileage? I have a 40 gallon tank with only a fuel pressure gauge. I don't even think about gas mileage anymore.

All in all, it seems to me that a properly matched five speed (one where all of the gears, including first, are usable) with a big block is simply undoing part of the benefit of the big block...using torque instead of shifting. If you're going to be on long drives at 70 mph+ for a majority of the time, consider the Tremec. An alternative is the toploader with maybe 3.31s. some are trying even 2.88s.